A vacuum insulation panel and a refrigerator using a vacuum insulation panel is disclosed in Japanese Patent Laid-Open No. 2004-3534. The vacuum insulation panel described in FIG. 1 and the specification of Japanese Patent Laid-Open No. 2004-3534 has a depressed portion for holding a getter material. The depressed portion is formed on a joint surface of at least one of plural boards made of inorganic fiber shaped by heating and pressurization. Such an arrangement is to prevent the getter material from projecting and damaging an outer cover of the vacuum insulation panel.
FIG. 1 and the specification of Japanese Patent Laid-Open No. 2002-48466 describe a vacuum insulation panel to be installed in space, where foam insulation material is also filled, formed by an outer box and an inner box. The vacuum insulation panel includes a getter material which adsorbs moisture and an envelope made of film having a gas-barrier characteristic. No fixed structure such as a fixed member or a depressed portion is used to hold the getter material. The getter material is held between sheet-shaped compacts of inorganic fiber used as core material. The getter material thus held does not move between compacts. It stays in a prescribed position during a process, for example, for air evacuation for producing a vacuum insulation panel, so that cost reduction can be promoted.
The vacuum insulation panel described in FIG. 1 and the specification of Japanese Patent Laid-Open No. 2004-218747 includes a core, a getter material, and an envelope accommodating the core and the getter material. The getter material is put in a depressed portion formed on the core. The envelope whose inner surface faces the getter material is made of a laminate film having an aluminum foil layer. A highly pierce-resistant protective sheet is placed between the getter material and the envelope to prevent the envelope from being punctured when it is vacuum-sealed.
The vacuum insulation panel described in FIG. 1 and the specification of Japanese Patent Laid-Open No. H4(1992)-337195 includes a container whose interior is kept in vacuum, an inorganic fiber mat put in the container, and an inner film bag which is used to temporarily place the inorganic fiber mat in a compressed state. This composition of the vacuum insulation panel is to prevent the vacuum insulation panel from getting wrinkled, warped or bent.
Patent Document 1: Japanese Patent Laid-Open No. 2004-3534
Patent Document 2: Japanese Patent Laid-Open No. 2002-48466
Patent Document 3: Japanese Patent Laid-Open No. 2004-218747
Patent Document 4: Japanese Patent Laid-Open No. H4(1992)-337195
It is known that, generally, a core to be used in a vacuum insulation panel is dried to remove moisture and gas from it before it is subjected to a process performed to evacuate air from it. This is done not to allow, even in a high degree of vacuum, moisture and gas to get out of the core and lower the degree of vacuum there. It is also well known that, to adsorb a very small amount of moisture and gas getting out of core material while the core is kept in a high degree of vacuum for a long period of time, a getter material such as a synthetic zeolite or activated carbon is put in the vacuum insulation panel. The core having been dried, therefore, requires to be put in a state, for example, in vacuum free of moisture and gas so as not to allow it to adsorb moisture and gas from outside.
The vacuum insulation panels described in Japanese Patent Laid-Open Nos. 2004-3534, 2002-48466, or 2004-218747 have one of a construction in which a getter material is accommodated between plural core boards, a construction in which a getter material is held between sheet-shaped compacts, and a construction in which a getter material is covered with a protective sheet. Producing the vacuum insulation panels therefore involves a process for accommodating the getter material, for holding the getter material, or for covering the getter material with a protective sheet. During the process, it is possible that the core composed of core boards or sheet-shaped compacts adsorbs moisture and gas from the outside air.
The problems as described above will be explained in more detail with reference to FIG. 7 showing an explanatory block diagram of a conventional vacuum insulation panel. Referring to FIG. 7, a vacuum insulation panel 1 includes plural core materials 2a and 2b, an envelope 3, and a getter material 4. A depressed portion 5a is formed approximately at a center of the joint surface between the core materials 2a and 2b. The getter material 4 is accommodated in the depressed portion 5a. The getter material 4 can be placed in the core by raising one side of the core material 2b and placing the getter material 4 in the depressed portion 5a. Or, it is necessary to remove the core material 2b, place the getter material 4 in the depressed portion 5a formed on the core material 2a, and put back the core material 2b to cover the getter material 4. In either way, to place the getter material 4 in the core takes time and, during the time, the core materials 2a and 2b possibly adsorb moisture and gas from the outside air.
How to concretely deal with the above problem is not proposed in any of the Japanese Patent Laid-Open Nos. 2004-3534, 2002-48466, and 2004-218747 in which conventional techniques are described.
When the above-described type of cores are to be used inside insulation walls of, for example, a refrigerator, it is necessary to prepare the cores in plural sizes according to the size of the refrigerator or according to the sizes, including the thicknesses, of the insulation walls. In such a situation, it becomes necessary during a production process to put unfinished cores in storage. As previously mentioned, however, the cores coming through a drying process require to be swiftly put in vacuum so as not to adsorb moisture and gas from outside. Hence, a production process for a vacuum insulation panel which includes a core constructed as described above is designed without much flexibility and room for adjustment.
How to concretely deal with the above problem is not proposed in any of the Japanese Patent Laid-Open Nos. 2004-3534, 2002-48466, and 2004-218747 in which conventional techniques are described.
In the Japanese Patent Laid-Open No. H4(1992)-337195 in which a conventional example is described, no concrete way to deal with the adsorption of moisture and gas from outside to the inorganic fiber mat put in the accommodating member is disclosed.
The present invention addresses the above problems with conventional vacuum insulation panels. It aims to reduce the adsorption of moisture and gas from outside to core materials while they are in a production process or in storage in an unfinished state.